State of the art research in the treatment of chronic diseases is based on the development of controlled release systems capable of delivering drugs rapidly and efficiently to where they are needed. A major requirement is that these devices should insure delivery and penetration of the drug to the active site. New nanostructured materials represent an efficient way to administer medications and biological products in future applications1-5. Hydrogels based on N-isopropylacrilimide and metacrilic acids (MAA) have recently received considerable attention. This is due to their ability to swell in response to the stimulation of the medium6-8. In the solid state, the existence of interpolymeric complexes in which monomers are linked together through hydrogen bonds has been observed. These linkages occur under acid conditions and are stabilized through hydrophobic interactions. This leads to a marked dependence on the pH of the medium in which swelling occurs. This swelling is also strongly dependent on the degree of cross-linking. The use of drug delivery by oral means has received considerable attention, particularly in cases in which activation is controlled by variations in the pH. Copolymers having a high concentration of N-isopropylacrilamide appear to be the most effective in enabling one to obtain different cut-off curves used in the drug model.12-15 
In the majority of cases, which involve controlled drug release, the medication or other biological agent, is introduced into the interior of the reservoir normally known as the transporter. The transporter usually consists of a polymeric material. Under normal conditions the rate of drug release is controlled by the properties of the polymeric material which constitutes the transporter. However, other factors may also be rate determining. When these factors are taken into account, it may be possible to insure a slow, constant rate of drug delivery over extended periods of time.16-18The use of these materials has lead to considerable advances in drug delivery when compared to systems currently in use. In conventional drug delivery systems, drug concentrations reach a maximum value only to decay, finally reaching a concentration, which requires the administration of another dose. Additionally, if the maximum drug concentration exceeds the safe level or if, alternatively it falls below the required dose, cyclic periods will occur during which the drug is not producing the desired effect. This is generally known as “variations in tisular exposure”. When controlled drug release is used, it may be possible to maintain drug concentrations, which fall between the maximum allowed rate, and the minimum concentration at which the rate is effective19-21.
In order for the drug to be delivered to the desired site, diffusion from the surface of the transporter to the medium surrounding the transporter must occur. From this point, the drug must diffuse over an area in which it will be effective. Following many studies, it has been concluded that there are four general mechanisms by which controlled drug release can be classified: 1) diffusion controlled systems, 2) chemically controlled systems, 3) systems activated by a desolubilizer and, 4) systems which are magnetically controlled.
The migration of a drug to a fluid medium for a system such as that described here, must involve a process in which the drug is desorbed from the surface of the transporter and is simultaneously absorbed into the fluid medium. This process is controlled by a concentration gradient. The fluid might consist of either water or a biological fluid. The entrance of a solvent into a polymer, which is in a vitreous state, may produce a considerable increase in the macromolecular motion. From a thermodynamic point of view, a solubility parameter d, and the interaction between the material and the solvent c, can express the compatibility between the solvent and the reservoir. If the solid is only slightly compatible with the polymer, it will remain in the vitreous state and under these conditions the controlled release of any drug will be very slow and of limited pharmacological use. On the other hand if the thermodynamics are favorable, the probability that the solute can diffuse from the transporter to the fluid is very large (Korsmeyer and Pepas, 1984 and Lee 1985a).22 In 1971 Yasuda and Lamaze refined their theory on free volume and noted that they could predict the diffusion coefficient of a drug across a polymeric matrix with considerable accuracy23. In this treatment they showed that the normalized diffusion coefficient of the solute in the polymer and the diffusion coefficient of the solute in the pure solvent are related by the extent of hydration. The external transport of the drug is caused by the dissolution of the solute at the interface between the solute and the reservoir followed by external diffusion under the influence of a concentration gradient, which obeys Fick's first law (Langer and Peppas, 1983)24. These systems are capable of drug release at a constant rate. However, in practice factors exist which may lead to large deviations. This problem can usually be corrected by adjusting or changing the geometry of the device. When the system is a monolith, the active compound is uniformly distributed on the support of the solid polymer.
The drug may be dissolved within the polymer matrix or dispersed depending on whether its concentration is such that its solubility in the polymer has been exceeded. The migration of the drug to the fluid medium occurs as a result of molecular surface diffusion along the support or by pore diffusion through the micro and meso pores within the matrix of the polymer. In this case, diffusion can be interpreted using Fick's second law. However, in any case the migration of the drug to the fluid medium will decrease as a function of time. This decrease occurs as a result of an increase in the length of the diffusion path25 (Rhine et.al., 1980).
The drug is chemically bound to the polymer chain and is released as a result of a hydrolytic cleavage. The rate of drug release can be altered if the hydrolysis can be catalyzed by enzymes (Kopeck et. al, 1981)26. Other systems of continual drug release include polymers formed from polylactic acid and its copolymers30. These precursors, together with glycolic acid have been used primarily due to their biodegradabilility and biocompatibility. The microencapsulation of drugs31-32 from a technical point of view can be defined as a process, which involves the covering of drugs. This may occur as molecules, solid particles or liquid globules. The materials used in the encapsulation process will depend on the particular application. However, the process will give rise to particles having micrometric dimensions. The products, which are formed as a result of this process, are referred to as “microparticles”, microcapsules'or “microspheres”.
These systems differ in their morphology and internal structure. However, they are all similar in size which is approximately 1 mm33-34. When the particle size is less than 1 μm, the resultant products of the microencapsulation process are referred to as “nanospheres”, “nanoparticles” or nanocapsules”35-37. An important feature of the microencapsulation process is that the products are not limited to drugs or biological materials but are extended to include products in such areas as agriculture, cosmetics and food38.
There are other areas in which controlled drug delivery is used. These include medications, which are absorbed through the skin. Creams and gels, which can be applied to the skin, have been used for many years as sedatives and medications to eradicate localized infections. They can also be used to treat the entire body (systemic)39. An increasing number of medications have recently become available as transdermal patches. They adhere to the skin through an adhesive ring while a thin film of the medication40 covers the center of the patch. The medication is slowly absorbed through the skin until it is absorbed into the blood stream. The transdermal patches most frequently used include testosterone, estrogens, sedatives, birth control and nicotine patches (used to aid smoking cessation). Other patches such gabapentin deliver anticonvulsant medications (Neurontin)41-43. In some cases, the active medication is mixed with another substance that controls the rate at which it is absorbed. This means that they can be used continually for longer periods of time or even for several days.
Another method by which transdermic administration is applied makes use of small receptacles, which use air pressure to inject a small stream of medication through the upper layers of skin. People who require insulin on a daily basis can make use of some very small receptacles to administer the medication44. Researchers involved in gene therapy to treat HIV have experimented with this technology to inject genetic materials through the skin or muscle tissue45-46. Medications can also be delivered through mucous membranes. A large number of the drugs are administered through the lungs or through the nasal passage and are rapidly absorbed into the blood stream. A large gamut of medications, including painkillers and vaccinations can be applied using this technique. In what promises to be a significant advance in the treatment of diabetes, a new technique, which makes use of inhalation technology, is being tested. Patches can also be adhered in the mouth at the interior of the cheek muscles47-50.
In order to avoid the formation of a spinel, the sol-gel technique can be used as a good method by which the various solid phases can be controlled (T. Lopez et.al., Catalysis Today 35, 293, 1997). A greater degree of control can be achieved in comparison to other methods of synthesis. One can tailor make the reservoir to fit specific applications by using this method. Advances include:    (i) Superior homogeneity and purity    (ii) High biocompatibility with brain tissue    (iii) Better nano and microstructural control of the polymeric reservoir.    (iv) Greater BET surface area.    (v) Improved thermal stability of the drugs attached to the reservoir.    (vi) Well-defined pore size distributions.    (vii) The ease by which drugs can be attached and released from the reservoir.    (viii) Inorganic chain structures can be generated in solution    (ix) A finer degree of control over the hydroxylation of the reservoir can be achieved.
The process of reservoir fabrication has as an objective the optimization of the following variables: particle size, mean pore size, interaction forces and the degree of functionalization. It may also be desirable to modify the textural and electronic behavior of the reservoir.
Titania is a material, which has important applications in industry. As an example we cite the synthesis of hydrocarbons from carbon monoxide or synthesis gas (U.S. Pat. No. 4,992,406; U.S. Pat. No. 4,794,099; U.S. Pat. No. 5,140,050; U.S. Pat. No. 521,553; U.S. Pat. No. 6,124,367.
Due to its unique electronic properties it has been used to modify the electronic properties of a transition metal when it is used as a reservoir (Klein L. C., Sol-Gel Technology for Thin Films, Fibers, Perform, Electronics and Shapes, (Noyes: New: New Jersey 1997)
Under conditions of normal atmospheric pressure, titania can have three different crystal phases: brookite, anatase and rutile. In all three phases, the Ti atoms are centered inside deformed oxygen octahedra. The number of edges of these octahedra that are shared distinguishes the different crystalline phases. Three octahedral edges are shared in brookite, four in anatase, and two in rutile (L. Pauling, JACS 51 (1929) 1010. This results in a different mass density for each phase. Pure titania with a large crystallite size is stoichiometric, dielectric and not useful in catalysis. It is necessary to change the stoichiometry by creating oxygen vacancies or other bulk defects.
The electronic and catalytic properties of titania depend on the local density and on the type of impurities present in the crystal structure (R. H. Clark “The chemistry of Titanium and Vanadium, Elsevier Publishers Co. N.Y. 1968, Ch 9).
Sol-gel technology is an important synthesis method by which the crystalline phases and particle size of titania can be controlled. A sol is a fluid, colloidal dispersion of solid particles in a liquid phase where the particles are sufficiently small to stay suspended in Brownian motion. A “gel” is a solid consisting of at least two phases wherein a solid phase forms a network that entraps and immobilizes a liquid phase.
In the sol-gel process the dissolved or “solution” precursors can include metal alkoxides, alcohol, water, acid or basic promoters and on occasion salt solutions. Metal alkoxides are commonly employed as high purity solution precursors. When they react with water through a series of hydrolysis and condensation reactions they yield amorphous metal oxides or oxyhydroxide gels. When the volatile alcohol's are removed the result is the formation of crystalline solid compounds.
The materials that are used as colloid precursors can be metals, metal oxides, metal oxo-hydroxides or other insoluble compounds. The degree of aggregation or flocculation in the colloidal precursor can be adjusted in such a way that the pore size distribution can be controlled. Dehydration, gelation, chemical cross-linking and freezing can be used to form the shape and appearance of the final product. Some advantages using sol-gel technology include control over the purity of the alkoxide precursors, control over the homogeneity of the product, control over the evolution of the desired crystalline phases and most importantly, the reproducibility of the materials synthesized.
For H2O/Ti(OR)4 ratios of between 0 and 0.1, the titanium alkoxide reacts immediately with water and alcohol. During the hydrolysis, the hexacoordination of the central titanium remains (T. Boyd, J. Polymer Sci., 7(1951)591). The hydrolysis product is not fully hydrolyzed nor can it ever be a pure oxide. It can only be in the form,TinO2n-(x+y)/2(OH)xOR)y 
Where n is the number of titanium atoms polymerized in the polymer molecule and x and y is the number of terminal OH and OR groups respectively. It is well known that some sol-gel structures attain their highest coordination state through intermolecular links (Sankar G., Vasureman S, and Rao C. N. R., J. Phys. Chem, 94, 1879 (1988)). Because there are strong Van der Wall interaction forces between the drugs and the titania reservoir, it is possible to encapsulate a large amount of medication within the titania reservoir.
Additional Titania Patents using Sol-Methods
U.S. Pat. No. 6,124,367. This patent protects reservoirs used in the Fischer Tropsch reactions from sintering by imparting a higher degree of mechanical strength to the reservoir. It incorporates SiO2 and Al2O3 into the reservoir and claims a rutile—anatase ratio of 1/9. It is a porous reservoir with either a spherical or a cylindrical shape. It is made by extrusion, spray drying or tableting.
U.S. Pat. No. 6,117,814. This patent describes a titania reservoir which also incorporates silica and alumina as a binder into the structure. The purpose of the binder is to impart better mechanical properties to the reservoir. The size range of this reservoir is from between 20 to 120 microns. The reservoir is approximately 50% binder, which is fabricated by a sol-gel process.
U.S. Pat. No. 6,087,405. This patent describes a reservoir to be used in a Fischer Tropsch gas synthesis reaction. The reservoir incorporates group VII metals into its structure. The rutile-anatase ratio in the structure is a distinguishing feature of this patent.